Not sure either, but I think he's comparing Rider to Shiroe there... taking into consideration how both their goals are extremely idiotic and their will and ambition to see it through is equally strong.Not sure what the Waver speech was supposed to be about. Is Waver a psychotic hero of justice too?
And just like Rider didn't regret what he did in life, Shiroe says that he won't regret his choice either.
I didn't like the ending *that* much... the reason for that is that Shiroe will end up as Archer no matter what. We see him throwing his life away. Sure, it's nice that despite all that'll happen to him, "he still believes in what is right", but other than "Durr, I wanna be the hero" we get nothing out of him as to why he decides to go through hell instead of a heavenly life with Rin (she failed to stop him btw :/).
Well, maybe he does that because now he can say "I was not wrong" after everything he said to Archer in the end, right? Pah...
Now that I think about it, the saddest part about it is that, sooner or later, Rin will end up alone as a Clock Tower mage. She basically said so herself when she mentioned that she'll end her journey there, marking the end of their relationship before it even began.